a) Field of the Invention
This invention relates to an afocal variation focusing system for use with mirrored optical systems, and especially for partially-obscured reflecting telescopical systems.
b) Discussion of the Prior Art
"Varios" and "variators" are well known and useful optical systems. Such systems have found use primarily in zoom lens systems and in projectors, for example, to change the size of a projected image on a screen, but not to focus the image. In many instances, such vario and variator devices have been used, in combination with a front refracting optical system and a rear system module in slide projectors. In some instances, they have been used in combination with both a front refracting system and a rear refracting system module. However, in all known instances such optical systems which incorporate vario and variator optical systems have been used with refractor optical systems to alter the size of an image or to focus it, but not to focus the image of a front partially-obscured reflecting telescopical system.
Afocal variators of the specific type described in the present application have been known and in commercial use and on sale, by themselves, for at least seventeen years, for example for use in projector lenses to alter the size of a projected image on a screen. However, while afocal variator optical systems of the specific type disclosed herein, have been previously known in the art, such afocal variator optical systems are not known to have been previously used in the art to focus partially-obscured reflective telescopical systems in the manner disclosed, provided and claimed by the present application, as opposed to the prior art use to alter image size, or to focus refractor optical systems in which the afocal variator is positioned between front and rear optical element modules, as distinguished from use with partially-obscured reflecting telescopical systems in which the rear module is not another optical element, but is a light-reactive material, located at the final focal plane. Many of the latter uses are taught by applicant in the Related Applications listed above.
It is thus seen that while the use of varios and variators, either alone, or in combination with either a front refractive optical system and a rear refractive optical system are known, they are not known to have been used in combination with a front partially-obscured reflective telescopical system to alter active focal length so as to act as a focusing system, as opposed to a system for altering image size or focus when positioned between the elements of a complete, operational refractive optical system.
In the past, where it has been desired to alter the focal length of partially-obscured reflecting telescopical systems, this has usually been accomplished by continuously or discretely changing the length of the optical system, or by changing the location of a mirror relative to the length of the optical system, or by changing the position of one mirror relative to another, or by moving a tube in or out to subtract or add mechanical length between one mirror relative to another. Additionally, lens systems have been used to either focally compress or focally expand the light path of such telescopical systems, but such lenses are formula-specific and alter the telescopical focus within predictable limits, becoming essential parts of the imaging system itself. Altering focal length of partially-obscured reflecting telescopes without utilizing the imaging system, or changing the length of the optical system, or changing the position or location of a mirror or mirrors within a partially-obscured reflective optical system has not been known in the prior art.
In other known prior art, Hillman U.S. Pat. No. 2,937,570 discloses a telescope system in which the image forming lenses are moved in order to focus the system. That is, focusing is accomplished by moving objective lens and focusing lens, which are part of the telescope's "formula-specific" objective imaging system. Focusing is not accomplished or taught to be feasible by moving a portion of an afocal variator, nor by moving a portion of any other non-image forming modular optical lens system. Furthermore, this reference discloses a "formula-specific" optical system in which the lenses are all calculated and assembled to work together to form a telescope. It does not include an independent optical lens system module which is non-image forming. It does not include a central afocal variator module which does not comprise a portion of the image-forming optics. If any of the movable lenses of any of the systems taught by Hillman were removed, the entire system would be affected, very probably to the point that the system would no longer function for its intended purpose.
Matsumura U.S. Pat. No. 4,318,585 discloses an optical system with an afocal focusing group, but in which the afocal focusing group is a Galilean telescope system rather than an afocal variator.
Quenderff French Patent 2,572,545 teaches the use of a zoom lens to make enlarged pictures, and also teaches the use of various art known mechanical devices for connecting together optical modules. However, it neither teaches nor suggests the use of an afocal variator module as a focusing element within a partially-obscured reflective optical system.